<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
      <li v-for="(item,index) in arr" :key="index">{{ item.name }}<button @click="buyBooks(item)">买书</button></li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr>
        <th>序号</th>
        <th>书名</th>
        <th>单价</th>
        <th>数量</th>
        <th>合计</th>
      </tr>
       <tr v-for="(item,index) in arr" :key="index">
        <th>{{ index++}}</th>
        <th>{{ item.name }}</th>
        <th>{{ item.price }}</th>
        <th>{{ item.count }}</th>
        <th>{{ item.price*item.count }}</th>
      </tr>
    </table>
    <p>总价格为:{{ CountPriceSum }} </p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
      count:0,
      // :0
    };
  },
  methods:{
    buyBooks(bookItem) {
     this.arr.filter(item => {
      if(item.name === bookItem.name) {
        this.count = item.count++
      }
    })
    }
  },
  computed:{
    CountPriceSum() {
      return this.arr.reduce((pre,item) => pre +(item.price*item.count) ,0 )
    }
  }
 
};
</script>